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	<h1>gSurf vers. 0.2.0 - for Python 3 and Qt5</h1>
	<p>
		License: GPL v. 3.0
		<br />by M. Alberti - <a href="mailto:alberti.m65@gmail.com">alberti.m65@gmail.com</a>
		<br />
		<br />Requires a working <b>Python 3</b> installation, with the following modules:
	</p>
	<ul>
		<li>numpy</li>
		<li>PyQt5</li>
		<li>matplotlib</li>
		<li>gdal</li>
	</ul>
	<p>
		File to run the application: <b>gSurf.py</b>
		<br />Example launching the app in the Linux shell:
		<br /><i>python3 ./gSurf.py</i>
	</p>

	<h2>Aim</h2>
	<p>
		This Python program allows to calculate the intersection points between a plane and a DEM.
	</p>

	<p>A presentation in Italian of the algorithm theoretical bases is in <i>
	<a href="http://gisoftw.blogspot.com/2011/12/intersezioni-tra-dem-e-superfici.html">
	Intersezioni tra DEM e superfici planari, un tema di interesse in geologia</a></i>.
	An example of application is described in <i><a href="http://gisoftw.blogspot.com/2012/01/gsurf-una-applicazione-python-per.html">
	gSurf: una applicazione Python per calcolare interattivamente l'intersezione fra piani e DEM</a></i>. 
	</p>

	<h2>GUI summary</h2>
	<p>
		The application functionalities, grouped by subject, are described. See the figure below for number references.
		<br /><br />
				<img width="650px" src="screenshot.png" />
	</p>
	<p>
		<b>1</b>
		<br />Commands for reading the input DEM (<i>crtl+D</i>) and an optional linear shapefile
		(<i>ctrl+P</i>), for instance of fault traces. It is also possible to save the intersections
		as a point shapefile (<i>ctrl+S</i>).
		<br /><br /><b>2</b>
		<br />Listing of input DEM and shapefile; control of their visibility and of the DEM colomap.
		<br /><br /><b>3</b>
		<br />Numerical tuning of the location of the "source point" (i.e., a point that lies in the plane to be created).
		In (6) there is also a button (symbol: <i>red circle</i>) that allows to locate the source point in the map.
		The elevation can be set to be equal to the local DEM elevation (option: <i>'fix to DEM'</i>).
		<br /><br /><b>4</b>
		<br />Regulation of the plane orientation, expressed by its dip direction and dip angle.
		<br /><br /><b>5</b>
		<br />Regulation of the visibility and the color of the plane intersections.
		When interactive calculations of intersections are slow, it is possible to stop (and then to resume) them so that
		plane orientation values or source point locations can be modified without the calculation-related delays.
		<br /><br /><b>6</b>
		<br />Navigation toolbar that allows to zoom, pan, save the map as an image, and also to set the source point location
		in the map (red circle).
		<br /><br /><b>7</b>
		<br />The map visualization area (the current interface is unchanged from vers. 0.1.2).
	</p>

<h2>Input</h2>

<p>
	A DEM can be read through the File menu (1, <i>ctrl + D</i>).
	An additional line shapefile, representing fault traces or tectonic lineaments,
	can be also imported and visualised (1, <i>ctrl + P</i>).
</p>

<p>Map can be zoomed, panned, etc. with the navigation toolbar buttons (6).</p>

<p>
	A plane position and orientation is defined through its "source point" coordinates (3, 6), i.e., a point contained by the plane,
	and its dip direction and dip angle, following the geological convention (4).
	The source point position can be directly set in the map using an ad-hoc button (red circle in 6). Alternatively, 
	it can be set or fine-tuned using the numeric spinboxes for x, y and z values (3). 
	Elevation values can be constrained to DEM elevation, by checking the "fix to DEM" checkbox (3).
</p>

<h2>Output</h2>
<p>
	Point intersections can be saved in a shapefile (1, <i>ctrl + S</i>), to be used for further analyses and visualizations.
	Each point stores the original (x,y,z) values and the plane dip direction and angle, so that different solution for different
	fault segments can be merged without losing the original information.
</p>
<p>
	Map images in many formats (PDF, png, etc.) can be created using the navigation toolbar "Save" function (6, right).
</p>
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